The subject matter disclosed herein relates to electrical discharge machining. Specifically, the subject matter disclosed herein relates to systems for performing electrical discharge machining in turbine components, e.g., gas turbine blades or buckets.
Electrical discharge machining (EDM) is a manufacturing process whereby shapes are formed in a subject material using electrical discharge (sparks). An electrode (also called a tool electrode) is placed proximate the subject material (also called a workpiece), and an electrical voltage is applied between the electrode and workpiece. When the intensity of the electric field between the electrode and the subject material exceeds the resistance of the dielectric medium, a current flows from the electrode to the subject material, or vice versa, removing some material from both the electrode and subject material.
Currently, EDM is the most reliable technology used to form cooling holes and fuel injection holes in turbine components (e.g., airfoils). As such, EDM is widely used to form these holes in turbine airfoils. However, EDM drilling is relatively slow, even when using a set of multiple electrodes. Further, several EDM machines are typically employed at one time in order to meet production time requirements, which occupies a significant amount of floor space in a manufacturing facility. Even further, in EDM machines employing grouped electrode arrangements, local debris drives the slowdown and withdrawal of not only one or more affected electrodes but also the entire group of electrodes including the unaffected electrodes. The entire group of electrodes feeds or withdraws together according to the worst case electrode (such as the electrode with the most debris buildup or shortest workpiece-electrode gap). As a result, the overall feed rate or machining productivity follows the lowest feed rate of the worst electrode with the most debris buildup or shortest gap at any given time.